Field of the Invention
The invention relates to a connecting element for connection of a first electrical shielding arrangement which is arranged around a line bushing, to at least one tubular isolating barrier which is arranged around the line bushing, and to at least one second electrical shielding arrangement, which is arranged around the line bushing and has at least one tubular isolating barrier which is arranged around the line bushing. The invention likewise relates to an electrical shield for a line bushing and to a method for production of an electrical shield for a line bushing.
The electrical connection of electrical installations, in particular of high-voltage installations, requires a large amount of technical complexity for the electrical shielding of the feeding and outgoing voltage lines. Particularly in the case of outgoers and bushings for electrical installations, electrical shielding must be provided at all times and over the entire line route. Particularly in situations in which the electrical installation is an oil-cooled transformer or an induction coil for high operating voltages, the line route is arranged in a grounded dome, which contains oil, of the corresponding electrical installation.
Electrical shielding of the line bushing is essential in particular for high DC voltages, such as those which occur in high-voltage direct-current transmission systems (HVDC). The electrical and mechanical loads which occur in this case must be compensated for by the oil-filled barrier system in conjunction with the tubular electrode at all times and for all possible voltage situations. This can be achieved only by means of a continuous barrier arrangement as an electrical shield around the line bushing.
For example, DE 690 24 335 T2 describes a bush for high DC voltages. According to the invention there, the electrical field is controlled capacitively by means of a capacitor body arranged around the disconnection point. In this case, a position in the axial direction with respect to the line bushing is defined as a function of the radii, arranged in one another, of the capacitor body, which position is in the form of a straight truncated cone aligned along the line bushing.
Furthermore, DE 690 12 258 T2 discloses a capacitor internal wall for field control of the line connection of a transformer bushing. According to the invention there, the capacitor isolating wall prevents any flashover of the electrical voltage, in that this barrier is suitable for capacitive and resistive control of the electrical field and is designed such that the voltages and field strength which occur in the respective area do not lead to destruction of the barriers.
The design of a high-voltage transformer, in particular of a HVDC transformer, is subject to the problem that the barriers of the electrical shielding must be shortened within a tank housing which remains unchanged because the transformer windings are becoming ever larger and because this results in the distance between the transformer windings and the tank wall becoming too short. The overlap, which is required for isolation reasons, between the shielding on the winding side and the shielding of the outgoer from the tank housing is therefore no longer provided without problems when using a conventional design.
All of the solutions in the prior art are subject to the disadvantage that conventional shielding arrangements around a high-voltage line bushing, in particular for HVDC applications, do not provide a complete overlap of the barrier systems of the shielding arrangements.